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Density Functional Theory Study of Elemental Mercury Adsorption on Fe2O3[104] and Its Effect on Carbon Deposit during Chemical Looping Combustion

Zhang, Junjiao, Qin, Wu, Dong, Changqing, Yang, Yongping
Energy & Fuels 2016 v.30 no.4 pp. 3413-3418
adsorption, carbon, chemical bonding, combustion, ferric oxide, iron, kinetics, mercury, methodology, synergism
This study investigated the adsorption of elemental mercury (Hg⁰) on perfect and reduced Fe₂O₃[104] surfaces as well as analyzed the synergistic effect of Hg⁰ on the catalytic decomposition of CO on the reduced surfaces using density functional theory calculations. This study aimed to clarify the correlations among Hg⁰ adsorption, CO decomposition, and Fe₂O₃ reduction degree. Theoretical results indicated that Hg⁰ underwent Fe top site adsorption to Fe bridge site adsorption as Fe₂O₃ was reduced into iron. This phenomenon increased Eₐdₛ with a local extreme of −2.063 eV for Hg⁰–Fe₂O₁.₃₆₄. The adsorption of Hg⁰ decreased Eₐdₛ for CO adsorption on the reduced Fe₂O₃ surfaces but promoted charge transfer from the surface to the adsorbed CO molecule. This event activated the C–O bond, favoring its decomposition. A kinetic model for catalytic CO decompositions with and without Hg⁰ further revealed the synergistic effect of Hg⁰ on carbon deposition and the relationship between the reaction rate and degree of chemical looping combustion.